Good afternoon, everyone. I'm Dr. Jessica Cross and I work for NOAA at the Pacific Marine Environmental Laboratory. I specialize in ocean acidification sciences, and specifically focus on how the observations that we make at NOAA, can help us understand the impacts of ocean acidification on ecosystems, and how those impacts can trickle up to human communities through impacts on different economies across the Arctic. Ocean acidification is caused by the buildup of carbon dioxide in the atmosphere. In short, as we emit more carbon dioxide into the atmosphere, the ocean then soaks up a really good portion of that, it's almost 22 tons every single day, and about one-third of it has been absorbed by the ocean so far. That's one-third of all of the carbon that we've emitted into the atmosphere, and that's great. It performs a really critical service for the planet, by storing some of that CO2 outside of the atmosphere where it could otherwise contribute to global warming. The oceans in this respect are really doing us a big favor, but once that carbon dioxide gets into the ocean, it causes a cascade of chemical reactions that can have really big implications for ocean biology. On top of that, some areas of the global ocean have a naturally high vulnerability to this atmospheric CO2, this atmospheric carbon dioxide, because there's already an awful lot of carbon dioxide in the ocean water to begin with, one of those places is the Arctic Ocean. When you combine these two aspects together, the anthropogenic or human caused carbon dioxide with the natural carbon dioxide that's in the ocean water and add them together, we can cross critical chemical thresholds that are referred to as ocean acidification events. The picture I'm showing on this slide is actually a subset of a much larger photograph, that was taken during Whale Fest in Alaska in 2012. A group of local fishermen used their fishing boats to spell out SOS in the water with acid ocean in the middle. It's not technically true that ocean acidification causes the ocean to become acidic, but it does cause the ocean to become more acidic than it was before, and these ocean acidification events can be really critical. Ocean acidification works or causes a reduction in the pH of the ocean by releasing hydrogen ions. This slide is showing a subset of how that process actually works. When carbon dioxide reacts with water, it reacts is a weak acid, and so it makes to bicarbonate ions by combining also with free carbonate that is already dissolved in the ocean water. So CO2 from the atmosphere, plus water that the ocean is definitely full of plus carbonate, which is already free floating in the ocean water makes to bicarbonate ions. Very quickly, those bicarbonate ions sometimes lose their hydrogen ions. The pH of the ocean is controlled by the number of free hydrogen ions that are floating around in the water. Those free hydrogen ions lower the pH, low pH is more acidic. This can also cause a really big problem for ocean biology. Organisms that are exposed to a reduced pH often lose shells that are made out of calcium carbonate because that carbon is being used to buffer the carbon dioxide plus water reaction as you can see right here. This is an example of one key organism, a pteropod. Pteropods are free-floating zooplankton that form the base of the food web for many fish. When pteropods are exposed to ocean acidification levels expected in the year 2100, very quickly, they can dissolve. The photo in the middle here is at the exposure of about 20 days to acidified conditions, you can see that the shell looks substantially more pitted than it does in the original shell on the very left, and then by 45 days, that shell has almost completely dissolved. Even though that experiment was conducted on ocean acidification levels by the year 2100, we know that dissolution is already taking place in the global oceans. This is a snapshot of several news in scientific articles that were released, showing that pteropods are dissolving under conditions that we already see right now. This is true near volcanic carbon dioxide vents. It's true in the Southern Ocean, and it's true here in the Pacific Northwest. A similar organism, oyster larvae, also experienced dissolution that caused a big hatchery collapse in the Pacific Northwest in 2012. Ocean acidification does not just impact organisms that build their shells out of calcium carbonate. It also impacts much larger organisms like adult crabs and fish, through a variety of different mechanisms. One of them is direct effects. That can include shell dissolution that is caused by these acidic conditions, but it can also reduce the growth rate of fish as they try to build their internal skeletons, which are also commonly built out of calcium carbonate. Additionally, food web effects can also limit the growth of populations. Ocean acidification food web effects can include, direct impacts on organisms like pteropods that larger fish are used to being able to eat. Ocean acidification can also impact sensory mechanisms in many fish. These sensory effects can cause a fish's brain to distort the signals between fear and safety. In particular, it seems to swap its responses to predators and prey. In other words, a fish that has stressed by ocean acidification will swim towards a threat, but away from its own prey, you can imagine that that can make it pretty hard to find food. Cumulatively over time, all of these effects will aggregate together and can have big implications on populations. Again, not just populations of small organisms, but populations of much larger organisms like fish too. Importantly, these impacts on big fish populations could threaten the security, the food security of many Arctic communities. In particular, this is very important for communities that rely on subsistence proteins for a primary portion of their diet, and one example of that you can see here, these are drying salmon. Salmon in the Arctic rely on pteropods a lot for their food sources. If declines in pteropod populations correlate with declines of salmon populations, that can mean the subsistence community loses a lot of its food security. One key fishery that could be impacted by ocean acidification are greenland shrimp. Shrimp shells are built from calcium carbonate, and so we know that ocean acidification could have a pretty big impact on these organisms. However, while this is a very well-studied fishery, especially in Norway and in the Atlantic Arctic sector, we don't know much about how ocean acidification might impact these organisms, or how it might impact the returns on the fishery. Because this fishery composes almost 40 percent of the Norwegian economy, it's really critical that we get a better idea of what these risks look like in the future. Arctic cod are another key species, they could be impacted by ocean acidification. In particular, cod are moving further north as temperatures warm, which means their food sources are changing as well as their geographic extents. We know that cod and their food sources are both impacted by ocean acidification. So it will be really critical to understand not just what cod are exposed to right now, but what they might be exposed to going forward. Alaskan king crab are also a very critical species that could be impacted by ocean acidification. Some estimates indicate that under current management scenarios, Alaskan king crab populations could be reduced by as much as 41 percent. So in addition to understanding the risks of ocean acidification, it's critical for us to also adjust our adaptation strategies, to include management that also takes into account this ocean acidification. Many communities asked me, "So what do we do, if ocean acidification is happening and we can't stop it because that carbon dioxide is already in the atmosphere?" They want to know what they can do to reduce these risks for their community or for their industry. The US Global Change Research Program came up with the US Climate Resilience Toolkit. It's toolkit you can find online that applies to any community, it is US specific though, and this Climate Resilience Toolkit goes through five key steps that your community can take to better understand the risks that you face from climate change. Here we'll apply it to ocean acidification. The first step is to assess risk. After that, you investigate any options you might have to reduce these risks, then you prioritize those options, plan for the future, and afterwards you take action. Sometimes that action is getting a better understanding of other risks or hazards that you might be exposed to, and so we say that the cycle loops back on itself and we go from taking action to exploring new hazards.
